Punakha: A glacial lake outburst in Bhutan has damaged infrastructure in the country's Gasa district and triggered flood warnings in the neighbouring Indian states of West Bengal and Assam. Thousands of people have been moved to safer locations in vulnerable areas of West Bengal as authorities in both countries monitor the possibility of further flooding.
The incident occurred on Thursday evening, October 29, at Shintaphu Lake in northwestern Bhutan. Floodwaters entered the Mo Chhu river system, raising concerns about communities and infrastructure further downstream.
The Gasa Tshachu hot springs, a popular natural attraction in Bhutan, were among the areas affected. Floodwaters damaged facilities at the site, while sections of the Punakha Gasa highway and the road towards Laya village were also affected. Part of the road leading to Laya was washed away, disrupting access to the settlement and forcing authorities to suspend traffic.
A solar irrigation system in Punakha district was also reportedly damaged by the floodwaters. Bhutan's state broadcaster reported that two temporary Bailey bridges may have been swept away by the strong currents. However, the full extent of the damage was not immediately known because of the difficult conditions.
No deaths or injuries had been reported in Bhutan as of Friday. The affected hot springs area had been evacuated before the floodwaters arrived, helping to prevent casualties.
The incident prompted Bhutanese authorities to alert India about the possible downstream impact. India's Central Water Commission issued a special flood advisory on October 29 after receiving information from the Indian Embassy in Bhutan. The advisory warned that floodwaters could reach the India Bhutan border within six to eight hours, potentially affecting Alipurduar district in West Bengal and Dhubri district in Assam.
Authorities in West Bengal placed several vulnerable areas on high alert and began precautionary evacuation measures. In Alipurduar district, approximately 4,000 to 5,000 people were moved to shelters, while more than 6,000 additional people were relocated to safer locations, according to a statement by the district's Superintendent of Police.
Cooch Behar district was also placed on alert, particularly in areas near the Sankosh and Raidak rivers. Tufanganj and other locations close to the Assam border were among the areas being monitored. Residents living near riverbanks and in low lying settlements were advised to remain alert and follow official instructions.
In Assam, Dhubri district was identified as particularly vulnerable because of its position along the downstream river system. The state disaster management authorities and emergency response teams were monitoring the situation and preparing to respond if water levels increased. However, the reported update indicated that evacuation operations had not started in Dhubri at that stage.
The flood threat is connected to a river system that flows from Bhutan into India. Water from the affected lake entered the Mo Chhu river system. The Mo Chhu meets the Pho Chhu at Punakha to form the Punatsangchhu, which is known as the Sankosh after it enters India.
Bhutanese authorities continued monitoring river levels and warning systems along vulnerable stretches. The country's National Centre for Hydrology and Meteorology was involved in monitoring the situation. Indian authorities also maintained precautionary measures in areas facing possible flooding.
The Punatsangchhu II hydropower project reportedly took precautionary measures by opening its dam gates and suspending power generation because of concerns about incoming floodwater and debris. The measures were intended to reduce risks to the project during the sudden rise in water levels.
Shintaphu Lake is among 17 glacial lakes in Bhutan identified as potentially dangerous. Such lakes form when melting glacier ice creates natural reservoirs in mountainous regions. They may be held back by barriers made of rocks, soil, ice and other glacial material.
A glacial lake outburst flood occurs when water is suddenly released from one of these lakes. The resulting flow can carry large amounts of water, mud, rocks and debris through mountain valleys, damaging roads, bridges, settlements and other infrastructure.
Bhutan's mountainous geography makes it vulnerable to such events. The Himalayan region has experienced growing concerns about glacial lake stability as glaciers retreat and new lakes form. However, the specific cause of the latest incident has not yet been conclusively established.
The Gasa Tshachu area has experienced serious flooding in the past. On August 26, 2021, a major flash flood affected the hot springs after the Mo Chhu River changed its course and swept through the area.
The latest incident has once again highlighted the flood risks faced by communities in Bhutan and downstream areas of India. Although precautionary evacuations and warnings have been issued, the full extent of the damage in Bhutan and the possible impact on Indian communities remain under assessment.
Authorities in both countries continue to monitor the situation and have urged people living in vulnerable areas to remain cautious and follow official safety instructions.